Borabenzene based olefin polymerization catalysts

ABSTRACT

Disclosed is a catalyst having the general formula ##STR1## where Q is a ligand containing the ring ##STR2## R is hydrogen, N(R&#39;) 2 , OR&#39;, or R&#39;, each R&#39; is independently selected from alkyl from C 1  to C 10 , aryl from C 6  to C 15 , alkaryl C 7  to C 15 , and aralkyl from C 7  to C 15 , each X is independently selected from hydrogen, halogen, alkoxy from C 1  to C 10 , dialkylamino from C 1  to C 10 , methyl, ##STR3## each R 1  is independently selected from halogen, alkoxy from C 1  to C 10 , and R&#39;, L is ##STR4## Q, or X, where L can be bridged to Q, B is an optional base, &#34;n&#34; is 0 to 5, and M is titanium, zirconium, or hafnium.

BACKGROUND OF THE INVENTION

This invention relates to catalysts useful in homo- and co-polymerizingethylene and other olefinic hydrocarbons. In particular, it relates tocatalysts containing a transition metal π-bonded to a ligand thatcontains a borabenzene ring.

Until recently, polyolefins have been primarily made with conventionalZiegler catalyst systems. These catalysts typically consist oftransition metal-containing compounds and one or more organometalliccompound. For example, polyethylene has been made using Zieglercatalysts such as titanium trichloride and diethylaluminum chloride, ora mixture of titanium tetrachloride, vanadium oxytrichloride, andtriethylaluminum. These catalysts are inexpensive but they have lowactivity and therefore must be used at high concentrations. As a result,it is sometimes necessary to remove catalyst residues from the polymer,which adds to production costs. Neutralizing agents and stabilizers mustbe added to the polymer to overcome the deleterious effects of thecatalyst residues. Failure to remove catalyst residues leads to polymershaving a yellow or grey color and poor ultraviolet and long termstability. For example, chloride-containing residues can cause corrosionin polymer processing equipment. Furthermore, Ziegler catalysts producepolymers having a broad molecular weight distribution, which isundesirable for some applications such as injection molding. They arealso poor at incorporating α-olefin co-monomers. Poor co-monomerincorporation makes it difficult to control the polymer density. Largequantities of excess co-monomer may be required to achieve a certaindensity and many higher α-olefins, such as 1-octene, may be incorporatedat only very low levels, if at all.

Although substantial improvements in Ziegler catalyst systems haveoccurred since their discovery, these catalysts are now being replacedwith the recently discovered metallocene catalyst systems. A metallocenecatalyst typically consists of a transition metal compound which has oneor more cyclopentadienyl ring ligands. They have low activities whenused with organometallic compounds, such as aluminum alkyls, which areused with traditional Ziegler catalysts, but very high activities whenused with aluminoxanes as cocatalysts. The activities are generally sohigh that catalyst residues need not be removed from the polymer.Furthermore, they produce polymers with high molecular weights andnarrow molecular weight distributions. They also incorporate α-olefinco-monomers well. However, at higher temperatures metallocene catalyststend to produce lower molecular weight polymers. Thus, they are usefulfor gas phase and slurry polymerizations of ethylene, which areconducted at about 80° C. to about 95° C., but they do not generallywork well in solution polymerizations of ethylene, at about 150° C. toabout 250° C. The polymerization of ethylene in solution is desirablebecause it allows great flexibility for producing polymers over a widerange of molecular weights and densities as well as the use of a largevariety of different co-monomers. One can produce polymers that areuseful in many different applications. For example, high molecularweight, high density polyethylene (PE) film useful as a barrier film forfood packaging and low density ethylene co-polymers with good toughnessand high impact strength.

SUMMARY OF THE INVENTION

We have found a new class of catalysts based on a bora-benzene ringstructure and containing a transition metal. The catalysts of thisinvention have unusually high activities, which means that they can beused in very small quantities. They are also very good at incorporatingco-monomers into the polymer. They have good activity at highertemperatures and are therefore expected to be useful in solutionpolymerizations of ethylene. Finally, some of the catalysts within thescope of this invention contain tertiary amine groups. It is surprisingthat these catalysts are effective because many amine-containingcompounds are known to be catalyst poisons.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The catalysts of this invention have the general formula ##STR5##

In the formula, Q is a ligand containing a bora-benzene ring. Abora-benzene ring has the structure ##STR6## where R can be hydrogen,N(R')₂, OR', or R', where each R' is independently selected from alkylfrom C₁ to C₁₀, aryl from C₆ to C₁₅, alkaryl from C₇ to C₁₅, and aralkylfrom C₇ to C₁₅. The R group is preferably --N(R')₂ or phenyl, as thosecatalysts have the best properties and, if R is --N(R')₂, then the R' in--N(R')₂ is preferably methyl. Examples of Q ligands include ##STR7##where "m" is 0 to the maximum number of substitutable positions, and ispreferably 0 as those catalysts are easier to make. Each R₁ isindependently selected from halogen, alkoxy from C₁ to C₁₀, and R'. Thepreferred Q ligands are bora-benzene, bora-naphthalene, andbora-anthracene because those catalysts are easier to prepare.

In the general formula, each X is independently selected from hydrogen,halogen, alkoxy from C₁ to C₁₀, dialkylamino from C₁ to C₁₀, methyl,##STR8## where "n" is 0 to 5 and preferably is 0. The X group ispreferably chlorine or methyl, as those catalysts are easy to prepareand have good properties.

Also, L in the general formula can be ##STR9## Q, or X. Preferably, L isQ, cyclopentadienyl, or chlorine because those catalysts are easiest toprepare and have good properties.

Optionally, L can be bridged to Q. Groups that can be used to bridge twoligands include methylene, ethylene, 1,2-phenylene, dimethyl silyl,diphenyl silyl, diethyl silyl, and methyl phenyl silyl. Normally, only asingle bridge is used in a catalyst. It is believed that bridging theligand changes the geometry around the catalytically active transitionmetal and improves catalyst activity and other properties, such ascomonomer incorporation and thermal stability.

The M group in the general formula can be titanium, zirconium, orhafnium, but is preferably zirconium as those catalysts have a goodcombination of high activity and good stability.

In the general formula, B is an optional Lewis base. Up to an equimolaramount (with M) of base can be used. The use of a Lewis base isgenerally not preferred because it tends to decrease catalyst activity.However, it also tends to improve catalyst stability, so its inclusionmay be desirable, depending upon the process in which it is being used.The base can be residual solvent from the preparation of the catalyst,or it can be added separately in order to enhance properties of thecatalyst. Examples of bases that can be used in this invention includeethers such as diethyl ether, dibutyl ether, tetrahydrofuran, and1,2-dimethoxyethane, esters such as n-butyl phthalate, ethyl benzoate,and ethyl p-anisate, and phosphines such as triethylphosphine,tributylphosphine, and triphenylphosphine.

Preparation of the Q ligand portion of the catalyst can be found in theliterature. See, for example, "Borabenzene Derivatives 21.2,4-Pentadienylboranes as Key Intermediates of a Novel Route toBoracyclohexadienes and Boratabenzenes. Structure of [Li(TMEDA)] (C₅ H₅BNMe₂)" by Gerhard E. Herberich et al., Organometallics (1993), pages2891-2893, herein incorporated by reference. In that article,2,4-pentadienylborane is reacted with a lithium amide in tetrahydrofuranin the presence of tetramethylethylenediamine (TMEDA) to form adimethylamino borabenzenyl lithium TMEDA complex having the formula##STR10## See also, "Reactions of the 9-Mesityl-9-boraanthracene Anion"by R. Van Veen and F. Bickelhaupt, Journal of Organometallic Chemistry,(1974), pages 153-165, which describes the formation of9-mesityl-9-boraanthracenyllithium. ##STR11## Other Q ligands can beprepared in an analogous manner or by other processes. The catalyst canbe made from the Q ligand by adding a suspension of an appropriatetetravalent metal compound to a solution of the Q ligand. This reactioncan occur at about -78° C. to about 50° C., but is preferably performedbelow 0° C.

Since the catalyst is normally used in conjunction with anorganometallic co-catalyst, it is preferable to dissolve the catalyst ina solvent in which the co-catalyst is also soluble. For example, ifmethylaluminoxane (MAO) or polymethylaluminoxane (PMAO) is theco-catalyst, then toluene, xylene, benzene, or ethylbenzene could beused as the solvent. Other suitable co-catalysts include aluminum alkylshaving the formula AlR' _(x) (R₂)_(3-x), where 1<×<3 and R₂ is hydrogen,halide, or alkyl or alkoxide from C₁ to C₂₀, such as triethylaluminumand ethylaluminum dichloride. The preferred co-catalyst is MAO as itresults in high activity and a polymer having a narrower molecularweight distribution. The mole ratio of the organometallic cocatalyst tocatalyst when used in a polymerization is generally in the range 0.01:1to 100,000:1, and preferably ranges from 1:1 to 10,000:1.

To enhance its properties, the catalyst can be used with an acid saltthat contains a non-coordinating inert anion (see U.S. Pat. No.5,064,802). The acid salt is generally a non-nucleophilic compound thatconsists of bulky ligands attached to a boron or aluminum atom, such aslithium tetrakis(pentafluorophenyl) borate, lithiumtetrakis(pentafluorophenyl)aluminate, aniliniumtetrakis(pentafluorophenyl)borate, and mixtures thereof. The anion whichresults when these compounds react with the catalyst is believed to beweakly coordinated to the metal-containing cation. The mole ratio ofacid salt to catalyst can range from about 0.01:1 to about 1000:1, butis preferably about 1:1 to 10:1. While there is no limitation on themethod of preparing an active catalyst system from the catalyst and theacid salt, preferably they are mixed in an inert solvent at temperaturesin the range of about -78° C. to about 150° C. They can also be mixed inthe presence of monomer if desired. The acid salt can be used incombination with the organometallic cocatalysts described earlier.

The catalyst and co-catalyst can be used on a support such as silicagel, alumina, silica, magnesia, or titania, but supports are notpreferred as they may leave contaminants in the polymer. However, asupport may be required depending upon the process being utilized. Forexample, a support is generally needed in gas phase polymerizationprocesses and slurry polymerization processes in order to control theparticle size of the polymer being produced and in order to preventfouling of the reactor walls. In order to use a support, the catalystand co-catalyst are dissolved in the solvent and are precipitated ontothe support material by, for example, the evaporation of solvent. Theco-catalyst can also be deposited on the support or it can be introducedinto the reactor separately from the supported catalyst.

Once the catalyst has been prepared it should be used as promptly aspossible as it may lose some activity during storage. Storage of thecatalyst should be at a low temperature, such as -100° C. to about 20°C. The catalyst is used in a conventional manner in the polymerizationof olefinic hydrocarbon monomers. While unsaturated monomers such asstyrene can be polymerized using the catalysts of this invention, it isparticularly useful for polymerizing α-olefins such as propylene,1-butylene, 1-hexene, 1-octene, and especially ethylene.

The catalyst is also useful for copolymerizing mixtures of ethylene withunsaturated monomers such as 1-butene, 1-hexene, 1-octene, and the like;mixtures of ethylene and diolefins such as 1,3-butadiene, 1,4-hexadiene,1,5-hexadiene, and the like; and mixtures of ethylene and unsaturatedcomonomers such as norbornene, ethylidene norbornene, vinyl norbornene,and the like.

The catalysts of this invention can be utilized in a variety ofdifferent polymerization processes. They can be utilized in a liquidphase polymerization process (slurry, solution, suspension, bulk phase,or a combination of these), in a high pressure fluid phase, or in a gasphase polymerization process. The processes can be used in series or asindividual single processes. The pressure in the polymerization reactionzones can range from about 15 psia to about 50,000 psia and thetemperature can range from about -100° C. to about 300° C. The catalystcan be used in a conventional manner in the co-polymerization of olefinmonomers such as ethylene, propylene, 1-butene, 1-octene, 1-hexene,norbornene, and norbornadiene.

The following examples further illustrate this invention.

EXAMPLE 1

This example describes the synthesis of (B-dimethylaminoborabenzene)cyclopentadienylzirconium dichloride, which has the formula ##STR12##where Cp is cyclopentadienyl and Me is methyl.

To a suspension of 0.56 grams (2.13 mmole) of cyclopentadienylzirconiumtrichloride (purchased from Strem Chemicals) in 15 ml of absolute ether,a solution of 0.61 g (2.51 mmole) of dimethylamino borabenzenyl lithiumtetramethylethylenediamine complex, (prepared according to thehereinabove-cited article by G. E. Herberich) in 10 ml of ether wasadded at -78° C. The mixture was warmed to room temperature and wasstirred for an additional 1 hour. After the volatiles had been removedin vacuo, the residue was washed with 30 ml of hexane and extracted with30 ml of toluene. The toluene was evaporated under reduced pressure togive 0.23 grams of a black solid. Proton NMR spectrum indicated thepresence of some impurities in the product.

EXAMPLE 2

This example describes the synthesis of cyclopentadienyl(9-mesitylboraanthracenyl) zirconium dichloride, which has the formula##STR13##

A solution of 9-mesitylboraanthracenyllithium in diethyl ether wasprepared by adding 1.0 mL of 1.6M n-butyllithium in hexanes to asolution of 0.47 g (1.6 mmol) of 9-mesitylboraanthracene in 18 mLdiethyl ether at -78° C., warming to room temperature, and stirring foran additional 2 hours. The solution was cooled to -10° C. and 0.42 g(1.6 mmol) of cyclopentadienylzirconium trichloride (Strem Chemicals)was added. The bath was then allowed to reach room temperature, and thereaction mixture was stirred overnight. The volatiles were removed invacuo to give a reddish brown powder. To this was added 20 mL drytoluene and the mixture ws filtered to give a clear yellow-orangefiltrate which was concentrated to give a brown foam. This was treatedwith dry hexane (20 mL) and the mixture filtered to give 0.26 g of alight tan solid. Proton NMR spectrum of the product indicated thepresence of some impurities.

EXAMPLES 3 to 17

Ethylene was polymerized using the catalysts of Examples 1 and 2.(Examples 3 through 13 and Example 20 used the catalyst prepared inExample 1 and Examples 14 through 19 used the catalyst prepared inExample 2.) The polymerizations were conducted in a stirred 1.7 literautoclave at 80° C. or 110° C. Dry, oxygen-free toluene (840 ml) wascharged to a clean, dry, oxygen-free reactor. MAO from Ethyl Corporation(10 wt% in toluene) was used in some of the polymerizations. Otherpolymerizations were conducted using PMAO from Akzo Chemical (25 wt% intoluene). The desired amount of MAO or PMAO to give the ratio shown inthe table which follows was added by syringe at 30° C. The reactor washeated to the desired temperature and sufficient ethylene was added tobring the reactor pressure to 150 psig. The reactor was allowed toequilibrate at the desired temperature and pressure. A solution ofcatalyst was prepared by dissolving 0.100 grams of product in 100 ml oftoluene. The amount of this solution needed to give the amount ofcatalyst shown in the table was used to start a polymerization. Ethyleneflowed into the reactor as needed in order to keep the pressure constantat 150 psig as polymer was produced.

At the end of 1 hour (less, if the activity was very high) the ethyleneflow was stopped and the reactor was rapidly cooled to room temperature.The reactor was opened and the polymer was filtered from the toluene.The product was dried overnight in a vacuum oven and weighed. Thefollowing tables give the reaction conditions and the results ofpolymerizations.

    __________________________________________________________________________      Reactor                                                                       Rx Temp                                                                            Time                                                                              H2 Amt      Co-monomer                                                                           Catalyst                                                                           Al/Zr                                                                              Co-                                   Ex                                                                              (°C.)                                                                       (min)                                                                             (mmoles)                                                                           Co-monomer                                                                           (ml)   (mmoles)                                                                           (Atomic)                                                                           catalyst                              __________________________________________________________________________     3                                                                              80   60  0    None    0     9.00E-03                                                                           1430 PMAO                                   4                                                                              80   60  0    None    0     4.50E-03                                                                           2870 PMAO                                   5                                                                              80   60  180  None    0     4.50E-03                                                                           2870 PMAO                                   6                                                                              80   60  0    Butene-1                                                                             20     4.50E-03                                                                           2870 PMAO                                   7                                                                              110  60  0    None    0     4.50E-03                                                                           2870 PMAO                                   8                                                                              110  60  0    None    0     4.50E-03                                                                           2870 MAO                                    9                                                                              110  30  30   None    0     4.50E-03                                                                           2870 MAO                                   10                                                                              110  60  0    Butene-1                                                                             20     4.50E-03                                                                           2870 MAO                                   11                                                                              110  60  90   Butene-1                                                                             20     4.50E-03                                                                           2870 MAO                                   12                                                                              110  30  90   Hexene-1                                                                             20     4.50E-03                                                                           2870 MAO                                   13                                                                              110  60  0    Octene-1                                                                             20     4.50E-03                                                                           2870 MAO                                   14                                                                              80   30  30   Butene-1                                                                             17     4.79E-03                                                                           1570 MAO                                   15                                                                              80   15  30   Butene-1                                                                             17     4.79E-03                                                                           1570 MAO                                   16                                                                              80   30  30   Butene-1                                                                             17     4.79E-03                                                                           1570 MAO                                   17                                                                              80   30  30   Butene-1                                                                             17     4.79E-03                                                                           2190 MAO                                   18                                                                              110  10  0    Butene-1                                                                             17     4.79E-03                                                                           2190 MAO                                   19                                                                              110  30  0    Butene-1                                                                             17     2.87E-03                                                                           2190 MAO                                   20                                                                              80   60  0    5-vinyl-2-                                                                           30     3.00E-03                                                                           4500 MAO                                                   norbornene                                                    __________________________________________________________________________              Wt. PE                                                                             Cat Prod                                                                            MI2  MI20     Density                                    Ex.       (g)  (kg/g/hr)                                                                           (dg/min)                                                                           (dg/min)                                                                           MFR (g/ml)                                                                             Mw/Mn                                 __________________________________________________________________________     3        77.1 93.9  0.17 2.37 13.9                                                                              0.9574                                                                             2.00                                   4        81.3 198.1 0.14 2.57 18.0                                                                              0.9587                                                                             1.75                                   5        92.5 225.4 10.28                                                                              333  32.4                                                                              0.9720                                                                             --                                     6        71.7 174.7 1.11 24.92                                                                              22.5                                                                              0.9323                                                                             --                                     7        70.4 171.5 1.10 22.64                                                                              20.6                                                                              0.9616                                                                             1.70                                   8        80.1 195.2 1.50 35.81                                                                              23.9                                                                              0.9637                                                                             1.84                                   9        105.0                                                                              511.7 18.40                                                                              539  29.3                                                                              0.9714                                                                             4.194                                 10        96.5 235.1 7.92 152  19.2                                                                              0.9448                                                                             --                                    11        110.0                                                                              536.1 41.94                                                                              1202 28.7                                                                              0.9521                                                                             --                                    12        138.9                                                                              676.9 16.27                                                                              588  36.1                                                                              0.9584                                                                             4.85                                  13        65.0 158.4 9.29 185  19.9                                                                              0.9515                                                                             --                                    14        31.8 145.7 549  --   --  --   --                                    15        34.5 316.1 <0.01                                                                              2.89 --  --   --                                    16        44.5 203.8 106  --   --  --   --                                    17        83.6 383.0 25.8 588  22.8                                                                              --   --                                    18        66.1 908.4 <0.01                                                                              49.1 --  --   --                                    19        33.2 253.5 <0.01                                                                              31.9 --  --   --                                    20        49.1 179.4 0.07 1.18 17.1                                                                              0.9415                                                                             --                                    __________________________________________________________________________

The melt index of the polymer was measured according to ASTM D-1238,Condition E and Condition F. MI2 is the melt index measured with a 2.16kg weight (Condition E). MI20 is the melt index measured with a 21.6 kgweight (Condition F). MFR is the ratio of MI20 to MI2. The polymerdensity was measured according to ASTM D-1505. The molecular weightdistribution of the polymer was measured using a Waters 150 C gelpermeation chromatograph at 135° C. with 1,2,4-trichlorobenzene as thesolvent. Both weight average molecular weight (M_(w)) and ratio of M_(w)to M_(n) (number average molecular weight) are used to characterize themolecular weight distribution. The table shows a high activity at 80° C.and little or no decline in activity at 110° C. (Examples 9 vs. 2).

The catalyst has excellent comonomer incorporation properties. Note theunusually high butene-1 incorporation in Examples 6 and 10 whichproduced relatively low polymer densities. In addition, the catalystreadily incorporates comonomers which are usually difficult tocopolymerize. This is exemplified by the copolymerization of ethyleneand 5-vinyl-2-norbornene in Example 20. In Example 3, the ratio of theweight average molecular weight to the number average molecular weight,which is an indication of the molecular weight distribution, wasmeasured as 2.00. An Mw/Mn of 2.00 indicates a very narrow molecularweight distribution.

We claim:
 1. A catalyst having the general formula ##STR14## where Q isa ligand containing the ring ##STR15## R is selected from the groupconsisting of hydrogen, N(R')₂, OR', and R', each R' is independentlyselected from the group consisting of alkyl from C₁ to C₁₀, aryl from C₆to C₁₅, alkaryl from C₇ to C₁₅, and aralkyl from C₇ to C₁₅, each X isindependently selected from hydrogen, halogen, alkoxy from C₁ to C₁₀,dialkylamino from C₁ to C₁₀, methyl, ##STR16## each R₁ is independentlyselected from the group consisting of halogen, alkoxy from C₁ to C₁₀,and R', L is selected from the group consisting of ##STR17## Q, and X,where L can be bridged to Q, B is an optional Lewis base, "n" is 0 to 5,and M is selected from the group consisting of titanium, zirconium, andhafnium.
 2. A catalyst according to claim 1 wherein M is zirconium.
 3. Acatalyst according to claim 1 wherein each X is chlorine.
 4. A catalystaccording to claim 1 wherein each X is methyl.
 5. A catalyst accordingto claim 1 wherein L is cyclopentadienyl.
 6. A catalyst according toclaim 1 wherein L is chlorine.
 7. A catalyst according to claim 1wherein Q is ##STR18## and R is --N(R')₂ or phenyl.
 8. A catalystaccording to claim 7 wherein Q is ##STR19##
 9. A catalyst according toclaim 1 wherein Q is ##STR20## where "m" is 0 to
 7. 10. A catalystaccording to claim 1 wherein Q is ##STR21## where "m" is 0 to
 9. 11. Acatalyst according to claim 1 in combination with about 0.01 to about100,000 moles of an organometallic cocatalyst per mole of said catalyst.12. A catalyst according to claim 11 wherein said organometalliccocatalyst is methylaluminoxane or polymethylaluminoxane.
 13. A catalystaccording to claim 1 in combination with about 0.01 to about 1000 molesper mole of said catalyst of an acid salt that contains anon-coordinating inert anion.
 14. A catalyst according to claim 13wherein said acid salt is selected from the group consisting of lithiumtetrakis (pentafluorophenyl) borate, lithium tetrakis(pentafluorophenyl) aluminate, anilinium tetrakis (pentafluorophenyl)borate, and mixtures thereof.
 15. A catalyst having the general formula##STR22## where Q is ##STR23## each X is independently selected from thegroup consisting of chlorine and methyl, L is Q, ##STR24## or chlorine,R is --N(CH₃)₂ or alkyl substituted phenyl from C₇ to C₁₅, and B is anoptional Lewis base.
 16. A catalyst having the general formula ##STR25##where Cp is cyclopentadienyl, Q is ##STR26## and R is --N(CH₃)₂ or alkylsubstituted phenyl from C₇ to C₁₅.
 17. A catalyst according to claim 16wherein R is --N(CH₃)₂.
 18. A catalyst according to claim 16 wherein Ris trimethyl phenyl.
 19. A catalyst according to claim 16 whichcomprises B-dimethylamino-borabenzene cyclopentadienylzirconiumdichloride.
 20. A catalyst according to claim 16 which comprisescyclopentadienyl (9-mesitylboraanthracenyl) zirconium dichloride.